An 18-year-old man was brought to the ED by EMS after suffering a stab wound to his left upper chest. He was awake and alert, complaining of pain to his chest. His initial vital signs were stable. His exam was significant for a wound to his left upper chest, just inferior to the clavicle in the mid-clavicular line. A FAST exam was performed, with parasternal and subxiphoid pericardial views of the heart. There was some confusion about the initial images, specifically whether a noted abnormality was in the pericardial or pleural cavity. The initial assessment was unclear, but it was noted that the right ventricle appeared full and without any mass effect.
I opened my FAST files a few months ago to share the case of a child with blunt abdominal trauma, highlighting the importance of being alert for more than just the typical anechoic, black stripe. (“The FAST Files: The Signs of Injury You Don't Expect,” EMN 2018;40:24; http://bit.ly/2H3JFWd.) This case is another, and looking at the images in hindsight, several things key to the diagnosis are clear. The subxiphoid image is unclear and difficult to assess, but there is clearly a space between the typically closely opposed area between the right ventricle and the diaphragm. (Image 1; video available at http://bit.ly/VideosSound.) The parasternal image shows a gray (hypoechoic) area deep in the left ventricle. (Image 2; video available at http://bit.ly/VideosSound.) Effusions are typically expected to be anechoic because they are usually liquid in density. This effusion, however, is composed of clotted blood, and appears more hypoechoic.
The effusion also appears somewhat different from expected, and the location of the hypoechoic area is critical to identifying it as pericardial and not intrathoracic. The descending aorta marks the key difference: Pericardial collections are anterior to the descending aorta, while pleural collections will extend deep into the descending aorta. Noting this would have given us a clue that this hypoechoic area was within the pericardial sac.
Relying on the fullness of the right ventricle also created a false sense of reassurance that the noted abnormality was not hemodynamically significant. The intrapericardial pressure rises very rapidly in acute pericardial effusions, and the signs that we look for in chronic effusions (mass effect on the right ventricle, IVC fullness, etc.) may not be present. Patients with acute effusions can go from stable to coding in no time.
Unfortunately, that's exactly what happened to this patient. He was initially stable and underwent a CT scan, which demonstrated multiple findings, including possible pericardial injury. The pericardial collection was not considered hemodynamically significant based on the initial ultrasound, so attention was first paid to other injuries. He coded a couple of hours after arrival. A large pericardial clot was discovered and removed when his chest was opened in the ED. He then regained pulses, and his right ventricular wound was repaired in the OR.
Awareness of the location of the abnormality and its hemodynamic significance in this case was critical. Pericardial effusions can take on a variety of appearances, and lack of signs of tamponade in an acute effusion should not be reassuring.